Conventionally, known examples of x-ray apparatuses include a transmission type microfocus x-ray generating tube (simply referred to as x-ray tube hereinafter) used in microfocus x-ray generating devices. This x-ray tube has large magnifying power and is super precise because it is small and thus the object being examined and the x-ray can be brought close together.
However, in this type of x-ray tube, the target is irradiated with an electron beam and x-rays are generated, and when the high power electron beam is irradiated on the small area of the target, most of the energy of the electron beam converts to heat, and target deterioration and the service life of the target are problematic. As a result, the transmission microfocus x-ray generating apparatus was configured such that the device can be opened, but the target must be replaced periodically, and the structure is large and complex and also costly.
In recent years, seal-off x-ray tubes have been developed which are small and have a simple structure. However, the service life is short because of thermal deterioration of the target, and the size of the focal point is 5 μm, and an input of about 2 W is the maximum for the target.
Thus, a known example of a structure for extending the service life of the target is one wherein: a cathode which irradiates an electron beam and a target which is irradiated by the electron beam from this target and generates x-rays are disposed in a vacuum vessel; the target is disposed so to be moveable in the direction orthogonal to the axial direction of the electron beam; the target is moved by a magnet which is in outside of the vacuum vessel; the position on the target that is irradiated by the electron beam is changed and when a particular position that is irradiated by the electron beam on the target reaches its lifespan, the target is moved by a magnet and the initial performance is restored (for example, refer to Jpn. Pat. Appln. KOKAI Publication No. 3-22331 (Pages 2 to 3 and FIG. 1)).
However, in order to move the target which is inside the vacuum vessel as described above, the target itself must be made moveable and a magnet for moving the target must be provided, and thus there is the problem that the structure becomes complex.